One common utilization of trunnion assemblies of the foregoing type is in the leaf spring suspension systems of heavy duty trucks and similar vehicles. If expensive down-time of the vehicles with which they are associated is to be avoided, such trunnion assemblies and the grease seals employed therein must function reliably and satisfactorily for long periods of time notwithstanding their exposure to extreme temperatures, dirt and other debris, and other adverse operating conditions. The seal employed in such an assembly, and more particularly within the annular space between the spindle component and the periphery of the bore of the housing component, must reliably perform multiple and somewhat inconsistent functions. During recharging of the grease housing, the seal should permit purging discharge of old grease from the housing as new grease is pumped under pressure into it. At all other times during use of the trunnion, the seal should prevent passage of the grease from the housing. Additionally, it should prevent passage of dirt and other debris into the housing. The seal should further be of economical manufacture, and capable of convenient installation both initially and on occasions when the same might be removed for purposes of inspection and/or replacement.